Like Senior Cinco said : both do the same thing.
If I'm right I think it's something like this, depending on the different enemie types and there resistances :
- A Warrior enemy have a higher Strength > so higher Melee Armour Rating > so better use Magic Damage weapons to kill them faster ... or Ranged damage (bow)
- A Mage enemy have a higher Intelligence > so higher Magic Armour Rating > so better use Melee Damage weapons to kill them faster ... or Ranged damage (bow)
- A Ranger enemy have a higher Dexterity > so higher Ranged Armour Rating > so better use Melee and/or Magic damage to kill them faster ...
But I think they're also enemies like Necromancers or Ranger's with magic spells ... or warriors using magic ... so then a Balanced weapon is the (al)most appropriate weapon .
There are balanced bows doing ranged + magic damage ...
Of course it depends also on your hero's stats which kind of damage get the highest boost (.. % to .. damage) ... for the best profit with a certain kind of weapon ... or magic spell .